Antioxidant peptides derived from the hydrolyzate of purple sea urchin (Strongylocentrotus nudus) gonad alleviate oxidative stress in Caenorhabditis elegans

The papain hydrolyzate prepared from purple sea urchin (Strongylocentrotus nudus) gonad exerts significant antioxidant activity. Through ultrafiltration, gel filtration and high performance liquid chromatography, the active fractions from the hydrolyzate were screened by alleviating paraquat-induced oxidative stress in Caenorhabditis elegans, and the peptide components were identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Two antioxidant peptides SnP7 (AAVPSGASTGIYEALELR, 1805.03 Da) and SnP10 (NPLLEAFGNAK, 1173.34 Da) exhibit significant antioxidant capacity, which reduce reactive oxygen species (ROS) level and the expression of superoxide dismutase-3 (SOD-3) and heat shock protein-16.2 (HSP-16.2) in oxidation-damaged nematodes. Further studies indicated that SnP7 and SnP10 induce DAF-16 nuclear translocation and the expression of stress-related genes such as sod-3. RNA interference (RNAi) suggested that peptide induced enhancement of resistance is dependent on DAF-16. Taken together, S. nudus antioxidant peptides might act through activate DAF-16 signaling pathway, and induce the expression of DAF-16 target genes that enhance antioxidant potential of organisms.